Hello. I'm Dr. Sandra Fryhofer. Welcome to Medicine Matters. The topic: a controversy that has gone on for more than 70 years. Does vitamin C work for preventing and treating colds? A study was recently published in the Cochrane Database of Systematic Reviews. Here's why it matters.
The common cold is common. There are over 200 different viruses that can cause them. It's a major cause of missing both work and school and the leading cause of acute morbidity and doctor visits in high-income countries. And because colds are caused by viruses, antibiotics don't help, but that does not stop the quest for a cure. Using vitamin C became particularly popular in the 1970s, when Nobel Laureate Linus Pauling gave vitamin C for colds his seal of approval, on the basis of early placebo-controlled trials.
That was then. Now, in this new review, 72 studies were analyzed. Only those using supplement doses of 200 mg or higher were included. The conclusion:
• First, for preventing colds -- 20 trials with more than 11,000 patients showed that for most people, vitamin C didn't help much. It reduced colds, but only by 3%. For those under high physical stress -- marathon runners, skiers, and soldiers doing sub-Arctic exercise -- the results were dramatically different. The extra vitamin C in these patients cut colds in half.
• Next, duration of symptoms -- nearly 10,000 colds and 31 studies. The conclusions: for adults, an 8% reduction in duration of cold symptoms and nearly twice that for kids, a 14% reduction.
• Finally, for severity of cold symptoms -- in kids, doses of 1-2 g daily seemed to help.
The bottom line: More randomized controlled trials are needed. But on the basis of the data so far, vitamin C doesn't do much to keep you from getting a cold unless you're seriously stressed.
On the other hand, it's cheap and relatively safe, although a recent study says it may increase risk for kidney stones. And it does seem to help a little with how long your cold lasts and how bad it is.
What are you going to tell your patients?
For Medicine Matters, I'm Dr. Sandra Fryhofer.
Medscape Internal Medicine © 2014 WebMD, LLC
Cite this: Vitamin C and Colds: The Bottom Line - Medscape - Mar 20, 2014.